To be honest, I wouldn't even want her to be a champion, but a recurring character in lore. She just wants to do her art and gets support by Vladimir for it (at least to 50% because every new Vlad-themed artwork that gets displayed in Noxus is a petty jab at the Black Rose), who does appear sincere as a lover of the fine arts. Not everyone needs to be a super powerful champion.
My guess on the open end is, that Vladimir tries to build up his own "faction" within Noxus that is a bit more personal than just a weird cult that likes him. However, as a nobleman he has STANDARDS, so he doesn't just hire some goons of the street, but goes after only the most promising artists who he then all gets to know personally. In the end he will have a small but extremly loyal group following him - and as a bonus, in time of peace he can just watch them make art. The loyality is the biggest resource in a conflict with organisations like the Black Rose, and he seems to know that an open break with Le Blanc will happen in the future.